In all the heme proteins there are groups on the distal side of the hemes which are in the immediate vicinity of any ligand which binds to the iron atom. The hydroperoxidases are heme proteins which catalyze the destruction of adventitious hydrogen peroxide. There is considerable evidence that in the hydroperoxidases the groups on the distal side of the hemes hydrogen bond with molecules coordinated to the heme iron. The hydrogen bonding appears to be important to the catalytic action of the enzymes. In other heme proteins the role of the distal residues is less clear. We propose to investigate the ability of distal groups to hydrogen bond with ligands coordinated to hemes preparing a series of metalloporphyrins which have globin like pockets containing polar groups. We intend to study the interactions of the polar groups with ligands such as CO, NO, O, and CN minus by measuring the infrared stretching frequencies of the ligands. In analogy with previous protein studies we expect to see significant shifts in the IR bands. ESR techniques will also be used to measure the coupling constants associated with the unpaired electrons in iron-No and cobalt-O2 complexes since these parameters should be markedly effected by hydrogen bonding. Finally, molecular structures of significant compounds will be determined by X-ray diffraction studies to show which atoms are involved in the hydrogen bonding. All of these studies are aimed at determining the importance of hydrogen bonding to the mechanism of action of the hydroperoxidases.